Buying another solar panel.

Submitted: Friday, Mar 08, 2013 at 20:31
ThreadID: 100977 Views:2317 Replies:5 FollowUps:16
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Been comparing 140 watt solar panels and without naming anyone, here is three sellers compared simply by multiplying length by width of there panels in mm. 802,800 872,960 966,368. Is it reasonable to assume all 140 watt mono panels will be a similar size as its a bit late to check the rated output after purchase.Seems to be a fair bit of size difference. All the three retail outlets have been mentioned on this forum recently as good places to purchase panels from.Any ideas .
cheers Graeme.
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Reply By: PeterInSa - Friday, Mar 08, 2013 at 21:10

Friday, Mar 08, 2013 at 21:10
4 or so years ago we purchased BP solar panels and a BP Controller thinking that BP (In OZ) were here to stay and their panel sizes would not change, just in case one failed or we had storm damage ( with the mounts stuck to the roof it would be hard to downsize/upsize). Hopefully BP 80w panels are still the same size but they have moved their manufacturing Plants to China I beliieve.

Incidentally back then each 80watt panel was $600. How prices have come down since.
AnswerID: 506363

Reply By: Ross M - Friday, Mar 08, 2013 at 21:50

Friday, Mar 08, 2013 at 21:50
G'day Graeme W
Something doesn't add up with your post.
It reads as though they are all 140watt panels with the areas of the first being 0.614sqm, the second 0.837sqm and the third 0.355sqm.
These are vastly different areas of panel to be the same output of 140Watts.

The last one is around half the first one and less than half the area of the second.
It seems to be comparing apple with melons and lastly grapes.
Can you shed more light on what it is you are asking?
For the areas to be so different, the efficiency of the smallest has to be more than double the second ones efficiency. Probably not true so I would be very wary until something is definitely proven to be true.

Ross M
AnswerID: 506369

Follow Up By: Member - graeme W (WA) - Friday, Mar 08, 2013 at 22:38

Friday, Mar 08, 2013 at 22:38
Hi Ross. Thats the length times width in mm so the first is smallest the last the biggest all with about the same rating.
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Follow Up By: Ross M - Friday, Mar 08, 2013 at 23:04

Friday, Mar 08, 2013 at 23:04
Graeme.
Is there a typo or something?
The first is 802x800 and the last is 966x368
Therefore 802x800 is 641sqm I made a typo up above. got the 4 and the 1 frack to bunt.
The last is 966x368 is 0.355sqm. So close to half size.
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Follow Up By: Member - graeme W (WA) - Friday, Mar 08, 2013 at 23:36

Friday, Mar 08, 2013 at 23:36
Thats the total Ross length times width 802.800 compared to 966.368 smallest to biggest not huge but enough to make a difference i would have thought
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Reply By: fisho64 - Friday, Mar 08, 2013 at 22:54

Friday, Mar 08, 2013 at 22:54
just bought a 120W with MPPT reg from Bit Deals off Ebay $170 delivered. All looks well built and does what its supposed to.
AnswerID: 506371

Follow Up By: Member - graeme W (WA) - Saturday, Mar 09, 2013 at 00:02

Saturday, Mar 09, 2013 at 00:02
Great example for my question. Your panel 120 watts measures 1340 x 1200 for a max power current of 6.7 amps. Same company 125 watt panel measures 1100 x 808 for a max power current of 6.97. This panel is way smaller in size but according to them is 5watts bigger.
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Follow Up By: luxtourer - Saturday, Mar 09, 2013 at 20:47

Saturday, Mar 09, 2013 at 20:47
Hi Graeme
If you're comparing the 120W folding panel, you should only double one of the dimensions of the single 60W panel. So 1340 x 600 or 670 x 1200, giving 804,000 sq mm. This is less than the single 125W panel area of 888,800 sq mm. Just going on area, you might expect the second to be about 130W, but there are also possible differences in the silicon coverage over the panel surface between the different panels. Efficiency differences might also explain the discrepancies between the panels you list in your original post?

Cheers, John


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Follow Up By: fisho64 - Tuesday, Mar 12, 2013 at 00:08

Tuesday, Mar 12, 2013 at 00:08
yes Graeme that is a point I brought up with Bit deals as their 140 and 120 watt panels have identical dimensions. I asked "your two panels are identical in size, and seem to have the same description and number of cells. What is different between the 120 and 140?".

The answer was "Size has nothing to dop with a panels output", which is true in different technologies but in that case they should have answered that its a different cell type though I dont believe it is.
So I bought the 120 watt and today I hooked it up and put my DC clampmeter on the lead by the battery. In the clouds it was running about 3-4 amps but when the sun was full and I had the panel aimed straight at the sun at 3.30pm it touched on 9 amps though generally was around 7.5-8. Voltage was about 14.8-15V but Im not sure of the voltage accuracy as my meter has a dicky lead.
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Follow Up By: Member - graeme W (WA) - Tuesday, Mar 12, 2013 at 12:31

Tuesday, Mar 12, 2013 at 12:31
Hi Fisho64. That seems a good output from a 120 watt panel which is rated at a about a max of 6.8amps. Mine has to fit in 1400 x 700 so might put that one in.
Cheers Graeme.
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Follow Up By: fisho64 - Tuesday, Mar 12, 2013 at 14:42

Tuesday, Mar 12, 2013 at 14:42
yeah I was a bit suprized, Im assuming my clamp meter is accurate but I might just rig it up again in a minute and do it again with a photo? Im not sure if I can post a pic here as I think I ever have.
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Follow Up By: fisho64 - Tuesday, Mar 12, 2013 at 15:39

Tuesday, Mar 12, 2013 at 15:39
Im getting 7.5 amps out of it now, and with my hot Waeco 50 plugged into the Load connection, there is 2.5 amps still going into the battery or 1 amp when its on turbo.
I did notice though that as others have said, there is 13.3 volts at the alligator clips and 14.1 at the regulator so I'll move the reg to the end of the leads which should then be able to fully charge my AGM
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Reply By: Dennis Ellery - Saturday, Mar 09, 2013 at 00:17

Saturday, Mar 09, 2013 at 00:17
I was informed by a solar system design engineer that, manufacturers may rate their panels using different standards.
For example take two manufactures of panels with a similar output - one may rate his panel at 140 watt and the other may take a more conservative approach and rate the same performance as 120 watt. I have seen panels that produce more than their rated output under ideal conditions.
Without comparing panels side by side, in the same conditions, there is no way of comparing apples with apples. Comparing size is a rough guide but not ideal in comparing output.
AnswerID: 506375

Follow Up By: Member - graeme W (WA) - Saturday, Mar 09, 2013 at 00:44

Saturday, Mar 09, 2013 at 00:44
Hi Dennis.
Guess the question now is how to buy then, on rated output or size. In my case i would rather pay a bit more to fit a higher rated panel in the same space if you only new the rated specs were acurrate which some how im biginning to doubt. The above example from bit deals where the panels look similar (same maker. ?) but very different sizes for similar output. Easy to test at home once purchased. Should be some sort of standard on this stuff.
Cheers graeme.
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Follow Up By: Allan B (Member, SunCoast) - Saturday, Mar 09, 2013 at 10:51

Saturday, Mar 09, 2013 at 10:51
Size DOES count! LOL
As Dennis says, vendors rate their panels without reference to a standard, so it is reasonable that a larger area will have a larger output. Of course that comparison only applies at the same point in time of technical development as newer panels are more efficient than older.
Cheers
Allan

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Follow Up By: Dennis Ellery - Saturday, Mar 09, 2013 at 11:27

Saturday, Mar 09, 2013 at 11:27
Hi Graeme
If you go for a well-known brand like Sharp, BP and others who have been making panels for decades then you might have more confidence in their ratings, but you will pay more for them. This doesn’t mean the newer manufacturers are a lesser quality product though.
Best of luck.
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Follow Up By: Member - graeme W (WA) - Tuesday, Mar 12, 2013 at 12:56

Tuesday, Mar 12, 2013 at 12:56
Hi Dennis. Narrowed it down to thee bit deals 120 watt as it is a bigger panel than the marsol 120 watt.From fisho64s post looks like it may produce more than the rated amps.Cant find a 140 watt the right shape anyway.
Cheers graeme.
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Follow Up By: fisho64 - Wednesday, Mar 13, 2013 at 04:22

Wednesday, Mar 13, 2013 at 04:22
Bit deals do a 140 as well but same size. Make sure you get the newer one with MPPT reg
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Reply By: MEMBER - Darian, SA - Saturday, Mar 09, 2013 at 11:39

Saturday, Mar 09, 2013 at 11:39
I just bought a 120W deluxe kit from one Ebay seller and I chose to pay at the high $ end of the kits on offer.... why ?..... because that seller included comprehensive detail on the performance specs of the regulator and panel, including photos of the specific items in the kit. I noticed with some other suppliers that 'vagueness and innaccuracy' plagues many of the adverts (could this be intentional ? :-o) ............ as for the dozens of spelling errors ?... Conflicting photos too within an advert show differing components for the same item..... email queries are replied to with non-answers that suggest they don't want to share detail or don't understand english ...? (could it be the former :-o).
AnswerID: 506393

Follow Up By: GLX3000 - Saturday, Mar 09, 2013 at 15:15

Saturday, Mar 09, 2013 at 15:15
Discovered the same sort of ebay-speak when looking to purchase. Eventually bought 2x75 watt panels from a Q'land seller. However, the panels could not open full 180 degrees because dome headed screws holding the hinges conflicted with their opposites. I had to remake the hinging by countersinking the hinge holes and using (stainless steel) c/sink screws. Cable was long enough but inadequate gauge. Clamps were sh*t, and although the panels came with a bag, there were no legs or stands with it. This I knew but did not fully appreciate the hassle making a set. One zip slider on the cover busted almost on the first day. BUT--- the panels have been pumping out good whenever the see the sun.
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Follow Up By: MEMBER - Darian, SA - Saturday, Mar 09, 2013 at 18:27

Saturday, Mar 09, 2013 at 18:27
Ah yes - funny that the kit design can be poor and the fittings can be junk but the panels work fine - from that we can reasonably presume that it is too expensive to set up for the manufacture of junk quality panels - the start point must be quite servicable panels and thereafter the $ games are played. Overstating the performance levels of particular panels (reported here and there) is another story of course.
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